A General Strategy for Nano‐Encapsulation via Interfacially Confined Living/Controlled Radical Miniemulsion Polymerization

Summary: We propose and demonstrate the utility of an interfacial living/controlled (reversible addition fragmentation chain transfer, RAFT) radical miniemulsion polymerization in nano‐encapsulation. The principles and methodology behind this technique are readily scalable and highly efficient. The living/controlled nature of the system offers great opportunities to tune the properties of the polymer shell‐like thickness, surface functionality, molecular weight, and inner‐wall functionality by simply using a semi‐continuous polymerization technique.

Illustration of encapsulation principles by RAFT interfacial miniemulsion polymerization.     

Polystyrene Microspheres and Nanospheres Produced by Electrospray

Summary: Polystyrene (PS) micro‐ and nanospheres with uniform dimensions and smooth surfaces have been produced by electrospray. The effect of PS molecular weight on beads morphology and the fundamental role of concentration have been investigated. Moreover, a new apparatus was designed to collect the polymer spheres during the process and to prevent the coalescence among the spheres.

PS micro‐ and nanospheres produced by electrospray     

One‐Pot Synthesis of Colloidal Nanobowls and Hybrid Multipod‐like Nanoparticles by Radiation Miniemulsion Polymerization

A facile approach is proposed to one‐pot synthesis of two kinds of nanoparticles: a new type of PS nanobowls (a hole appearing at the bottom of nanobowl) and PS/silica hybrid multipod‐like nanoparticles. The two type of nanoparticles generated together during polymerization could be separated easily by centrifugation. Furthermore, the structure of nanobowls could be easily controlled by the weight ratio of monomer/silica. In addition, we find that the multipod‐like nanoparticles play important roles in hydrophobic properties. The water contact angle increased from 24.0° to 143.3° after coated with the multipod‐like nanoparticles.

     

Preparation of Polystyrene‐Poly(N‐isopropylacrylamide) (PS‐PNIPA) Core‐Shell Particles by Photoemulsion Polymerization

Summary: Monodisperse thermosensitive PS‐NIPA core‐shell particles composed of a PS core and a cross‐linked PNIPA shell can be successfully synthesized by a novel method: photoemulsion polymerization. Cryo‐TEM images indicate clearly the core‐shell morphology of the PS‐NIPA particles: A homogeneous regular PNIPA shell has been affixed on the spherical PS core. DLS measurements indicate that the obtained PS‐NIPA latex particles are thermosensitive. The shell of PNIPA networks with different cross‐linking densities can shrink and re‐swell with temperature and the volume transition temperature is around 32 °C in all cases.

Cryo‐TEM image of PS‐NIPA core‐shell particles.     

Surface‐Active Gold Nanoparticles with Mixed Polymer Brushes as Surfactants in the Preparation of Polystyrene Colloid Particles

Gold nanoparticles with hydrophobic polystyrene (PS) and hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate] (PPEGMA) mixed polymer brushes are prepared. Different morphologies of the nanoparticles can be observed in chloroform (a common solvent for both of the polymers) and water (a precipitant for PS and a good solvent for PPEGMA). The nanoparticles can be used as surfactants in Pickering suspension polymerization. Upon addition of nanoparticles to a mixture of oil and water, the nanoparticles locate at the interface and the size of the oil droplets gets smaller. After polymerization of styrene oil droplets PS colloid particles with gold nanoparticles on the surface can be obtained.

     

In‐Situ Polymerization at the Interface of Micelles: A Novel Method to Control Functionality and Morphology

A new method to control the morphology and functionality of micelles is reported. Triblock copolymer micelles with atom transfer radical polymerization initiators at the interface are prepared in aqueous solution. After in‐situ polymerization at the interface, the structures of the interface and corona change, and micelles with PDMAEMA‐PEG comb–coil coronal chains are obtained. In aqueous solution, the pH exerts an influence on the morphology of the micelles. The coronal chains adopt different conformations at different pH values. Upon drying, the two coronal chains phase separate and form nanometer‐sized domains.

     

Hybrid Nanocomposite Films from Mono‐ and Multi‐Functional POSS Copolyacrylates in Miniemulsion

Summary: The synthesis of aqueous dispersions of hybrid acrylic copolymer particles with either a monofunctional or a multifunctional polyhedral oligomeric silsesquioxane methacrylate comonomer has been performed by free radical heterophase polymerization. The miniemulsion process gives stable latexes, whereas the less controlled emulsion route results in colloidal instability of the products. The thermal and mechanical properties of the nanocomposite latex films have been preliminarily investigated.

The nanocomposite latex particles based on hybrid copolyacrylates with highly dispersed POSS cages.     

Low‐Temperature Growth of Thick Polystyrene Brushes via ATRP

Summary: This contribution describes the graft polymerization of polystyrene (PS) by atom transfer radical polymerization at 50, 60, and 75 °C. Thick PS brushes were grown from initiator‐functionalized PGMA layers on silicon, and constant growth rates provide indirect evidence that the polymerizations were controlled.

Formation of polystyrene brushes at T < T_g by ATRP of styrene from α‐bromoester initiator‐functionalized poly(glycidyl methacrylate) layers.     

Synthesis of High Solid‐Content Latex using Alkali‐Soluble Resin as Sole Surfactant

Summary: A novel polymerization procedure to synthesize latex stabilized by alkali‐soluble resin (ASR) is detailed. According to this process, latexes with a high solid content and low viscosity are obtained using a substantially lower amount of ASR when compared with existing techniques. Similar rewet properties were found for the latexes obtained by a standard process and for the one obtained by the process described in this work.

Comparison of the particle size distributions obtained by conventional emulsion polymerization (○) and by miniemulsion polymerization (□).     

Ethylene and Ethylene/Propylene Polymerization Behavior of Bis(phenoxy‐imine) Zr and Hf Complexes with Perfluorophenyl Substituents

The catalytic properties of bis(phenoxy‐imine) Zr and Hf complexes incorporating perfluorophenyl groups with methylaluminoxane were investigated. The fluorinated complexes produced far higher‐molecular‐weight polyethylenes and ethylene/propylene copolymers with increased activities compared with the non‐fluorinated congeners. Moreover, the fluorinated complexes displayed a higher incorporation ability for propylene.

Structures of complexes 1 – 4 .     

Atom Transfer Radical Polymerization of Styrene and Methyl Methacrylate from Mesoporous Ordered Silica Particles

Summary: Mesoporous silica was used as substrate for the grafting of alkyl halides initiators. The control over the surface‐initiated polymerization of styrene and MMA, in terms of molar mass and molar mass distribution, was successfully achieved using an ATRP mechanism. The occurrence of the polymerization inside the mesopores was confirmed by thermogravimetric analysis.

Transmission electron microscopy and schematic representation of mesoporous silica functionalized by the anchored iniator (left) and the grafted polymer (right).     

Controlled Alternating Copolymerization of (Meth)acrylates and Vinyl Ethers by Using Organoheteroatom‐Mediated Living Radical Polymerization

Alternating copolymers comprised of (meth)acrylates and vinyl ethers with controlled molecular weights and polydispersities were synthesized for the first time by living radical polymerization using organotellurium, stibine, and bismuthine chain transfer agents. Combining living alternating copolymerization and living radical or living cationic polymerization afforded hitherto unavailable block copolymers with controlled macromolecular structures.

     

Continuous Production of Functionalized Polymer Particles Employing the Phase Separation in Polymer Blend Films

This study reports a continuous prepartion of spherical or hemispherical polymer particles simply utilizing the phase separation in polymer blend films during the coating process. We took an advantage of the strong phase separation between a water‐soluble crystalline polymer as a matrix and hydrophobic polymers as minor components. We demonstrated the prepartion of water‐soluble polystyrene (PS) particles, nitrilotriacetic acid (NTA)‐functionalized PS particles for protein separation, and semiconducting poly(3‐hexylthiophene) (P3HT) particles. The sizes of the particles could be controlled by adjusting the film thickness and weight fraction of the minor component polymers in the blend film. It provides a simple facile way to prepare polymer particles in a continous process.

     

Poly(dicyclopentadiene) Submicron Fibers Produced by Electrospinning

Summary: We have used the process of electrospinning to produce fibers of poly(dicyclopentadiene) with diameters on the submicron scale. The material, formed from a monomer‐catalyst solution, polymerized in flight during the electrospinning process. Fibers were collected over trenches etched in silicon and the Young's moduli were measured using an atomic force microscope to measure force‐displacement curves. The resulting values of Young's moduli are larger than typical values for bulk polymer material.

SEM image of suspended PDCPD fiber.     

Direct Synthesis of Biodegradable Polysaccharide Derivative Hydrogels Through Aqueous Diels‐Alder Chemistry

A robust synthetic strategy where polysaccharide derivative precursors react through aqueous Diels–Alder chemistry without the involvement of catalysts and coupling reagents, allowing for the direct encapsulation of positive and negative proteins within biodegradable hydrogels. The results demonstrated that the aqueous Diels–Alder chemistry provides an extremely selective reaction and proceeds with high efficiency for polysaccharide bioconjugation. This synthetic approach uniquely allows for the direct fabrication of biologically functionalized gels with ideal structures, which provides a competitive alternative to conventional conjugation techniques such as click chemistry.

     

Supramolecular Nanocycles Comprising β‐Cyclodextrin‐click‐Ferrocene Units: Rings of Rings of Rings

We applied 1,3‐dipolar cycloaddition to bind ethynylferrocene onto 6I‐azido‐6I‐deoxycyclomaltoheptaose under microwave assisted conditions. The process was investigated by ¹H NMR, FT‐IR spectroscopy, and MALDI‐TOF mass spectrometry. The ability of the synthesized compound to self‐organize to cyclic supramolecular structures was investigated by dynamic light scattering measurements and cryo‐transmission electron microscopy.

     

Bottom‐up Assembly of Poly(3‐hexylthiophene) on Carbon Nanotubes: 2D Building Blocks for Nanoscale Circuits

Hierarchical poly(3‐hexylthiophene)(P3HT)/carbon nanotube (CNT) supramolecular structures were fabricated through a bottom‐up CNT induced P3HT crystallization strategy. P3HT nanowires growing perpendicular from CNT surface have uniform width and height. The density and the length of these nanowires can be controlled by tuning the P3HT/CNT mass ratio. The quasi‐isothermal crystallization process monitored by in situ UV–Vis spectroscopy indicates that CNTs can greatly enhance the P3HT crystallization, and the P3HT nanowire formation follows first‐order kinetics. Such bottom‐up strategy provides a general approach to build 2D functional conductive supramolecular structures that will lead to numerous applications in nanoscale electronics.